Telephone system.



No. 877,121. PATENTBD JAN. 21, 1908.

H, M. POST.

TELEPHONE SYSTEM. APPLICATION PI EED NUV.11,1903.

2 SHEETS-SHEBT 1.

11m 121. PATEN ED JAN; 21 was PL M. 190w. L

TELBPEOHB SYSTEM.

APPLIOATIGN .FILED NOV. 11,1903.

2 SHEETS-SHEET 2.

UNITED STATES PATENT OFFICE.

HOWARD M. POST, OF CHICAGO, ILLINOIS, ASSIGNOR TO KELLOGG ,SWITGHBOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEiI-IONE SYSTEM.

Specification of Letters Patent.

Yatented Jan. 21, 1908.

T 0 all whom it may concern:

Be it known that I, Ilownnn M. PosT, a citizen of the United States of America, and resident of Chicago, county of Cook, and State of Illinois, have invented a new and usefulImprovement in Telephone Systems, of which the following is a specification My in vention relates to i mprovem ants in telephone systems of the common battery type.

It is often desired for various reasons to employ two sources of current at the central ollice, to supply the subscribers lines with current l'or conversation, one of these sources being connected with the calling lines and the other source being connected with the called lines. In the systems that have been heretofore devised for this purpose in which the .lines of each connection were so provided with current from the separate, sources, the battery connected with the calling line was disconnected when the operator inserted her cord circuit plug into the spring jack of the calling line thereby breaking the normal connection of said line with its source and again connecting a source therewith. In thus severing the normal connection of the. battery with the calling line, a disagreeable noise is caused in the waiting subscribers receiver.

One object of the present invention is to so arrange the said source of current and the apparatus at the central ethos that no great variationof potential takes place upon the calling line when the operator answers the call whereby the disagreeable noise in the subscribers receiver is prevented To accomplish this, I preferabl arrange the apparatus so that the normal connection of-the battery with the calling line remains undisturbed when the operatoranswers thecall, and at the same time the other source of current is connected with. the called line to supply current thereto for conversation.

In carrying out my invention, which is worked out for commercial purposes I so arrange the cut-oil relays of the lines which are ordinarily employed to sever the battery connection so that they do not respond when a connection for conversation is established with the calling line but do respond to sever said connection when the connection is completed with the called line. In the specific arrangement that I have worked out, I preferably also so arrange said cut-oli' relays asto connect the second battery with the called line when the connections are so completed.

Other objects .of my invention are to provide a system that is a practically and commercially operative one. that is simple and inexpensive to manufacture and install, and one that is efficient and durable in operation.

Still other objects and advantages will appear from the detailed description and c aims.

My invention is illustrated in the acoompanying drawing in which Figure 1 is a diagram of a telephone system showing my improvements applied to subscribers lines of the two-Wire type, and Fig. 2 is a similar diagram showing the invention applied to lines of the three Wire type.

The same reference letters are used throughout to designate similar parts.

Referring to Fig. 1, L and L indicate subscribers lines extending in two limbs 2 and 3 from their respective substations to the central ofiice where they terminate in the usual apparatus. cated any usual or desired common battery outfit by the ordinary signaling hell 4 and a condenser 5 in a permanent bridge of the line conductors and the transmitter 6 and receiver 7 in a second bridge which'is normally open at the switch hook 8.

At the central ofiice the line is provided, as is usual, with an answering jack J, and with a plurality of multiple jacks such as J and J in any number, andwith a line signal S, preferably in the form of a small incandescent lam The line conductors 2 and 3 are extends directly through to the corresponding tip and sleeve contacts of the answering jack J, the tip contacts of the multiple jacks being connected directly with the same line conductor, but the sleeve contacts. of the multiple jacks are connected by conductor 9 with the winding of a cut-off relay R and thence to the sleeve conductor 3, said relay R being shunted by a noninductive resistance 10 to permit the ready passage of the voice currents. The line relay R is provided with'a pair of balancing windings 11 and 12, the former being legged to ground by con- 7 ductor 13 from the sleeve conductor 3, and

the latter being 'oined upon one side b conductor 14 with t e line conductor 2 an n on the opposite side by conductor 15 wit a spring 16 of the cut-off relay R the normal contact of which is joined by a branch conductor 17 with the common lead orwiro 18 At the substation I have indinoticed substation with return over the seine psth through 11 oi the role-y circuit with the tine does not greatly change the pot .tisl upon said line and does not out e disturbance in the waiting suhscriioers r lesrning the party wanted, the line i is tested in the usual. msi'lner by touching the tip of the ceiling plug P to the test ring of one of the multiple jacks that line. it will be noted, that esid test rings are nosmclly connected to wound through winding 11 of line reia'y and since the tip of the wing is grounded through the test reluy 1 no flow of current results when an idic line is tested and the operator knows that the is not; busy. /Vhen l1 connection exists with the line, however, said sleeve rings are connected with the live pole of the battery 3*, through the sleeve strand oi -the inserted plug so that the touching of the tip of the testing plug to one of said test rings completes c path for current "from said buttery lillIOllglliESt relay T which is actuated to close the local circuit through the tertiery winding of the operators induction ,coil, thus causing s click in he receiver, and notifying herthet the line is busy. The connection of the testreloy st this time with the conductor 27 is made through the contacts 289i the listening key which is now in position to conmeet the operutors telephone with the cord circuit, before stated. Assuming that the line is ound idle, the calling plug P is inserted in one of the multiple ice-ks and the ringing key 38, 38 is operate- The insertion OI the closes a path for (1L1 "rent froin'thc buttery B the common wire 23, conductors 25 end .Zttluough the supervisory relay r, the strand 3' of the cord cirsuit, the slee e contacts of the plug and the multiple incl; into which it is inserted, the conductor 9 tin"; b. the winding of the cutoff relay ll and silence over the line conductor 3; and through conductor 13 including the "winding 11 of the line relay it to ground.

Current in th s path is sui'licient to actuate the said 0' 0-x relay, which opens the circuit of the line signal through its spring 20, thereby pret'a up; its operation during the connection am t the some time it serves through. the medium of its spring 16 to sever the connection with the battery B, and to connect-with the wire 212 leading to the common lead 23 ir un the l .tery B The line reluy B. may be siinult neously operated but does not result .ighting the signal lump S since its circuit is open at the contactsof thez oflice over the line conductor 3 and over the conductor 9 and thence through the forward portion of the sleeve strand 3 of the cord circuit, the conductors 39 and 23 and through the battery B to ground. The cut-off relay R is maintained actuated at this time by current from the battery B which flows through the wires 23 and 39, conductor 9, and thence through the winding 11 of the line relay R to ground. has been'culled but before his res onsc the supervisory relay r is actuated as efore described and serves to disconnect the conductor 2'7 and to complete the strand 1) for conversation. At the same time the local circuit of the supervisory signal S" is closed and since the supervisor relay 1" is not yet actuated, owing to the act that the subscribers line is still 0 en, said signal is lighted and indicates to t e operator that the called subscriber has not yet responded. Upon his re- After the subscriber" sponse said. relay r is actuated by current the line L during the connection of the cord circuit therewith and that the battery B alone furnishes current to the said line for conversation. Thus durin conversation the battery B, which is normal y connected with all of the lines, furnishes current over the calling subscribers line While the battery 13 is utilized for furnishing current to the called subscribers lines. It is apparent that the noise upon the calling subscribers lines is greatly reduced, if not entirely prevented, by the fact that the battery is permanently con nected therewith during the connection and is not severed and again connected. by the plugging in in response to his callf The switchboard foreach subscribers line, and in which the busytest contacts as well as It will be noted that the battery B is cut-ofl' from throughout the multiple section of the.

l toot of the ground spring; 60 of the out the finding oi. the cut-oil? reloy foreeeii. line,

V are included in the third eonduetor Whieh is separate from the telking eond'ueto're.

in this iiign re the subseribers lines are indicated etL end L the subscribers stations losing" the some as in the prior iigure and sit the central the lines one provided. with line signelsfiflwith answering jeelrs i end with multiple jocks-1J J in any desired num her. The line relay it is provided with one Winding 50 legged to ground. from the tip side of the'line end with o eeeonol Winding 51 included in e conductor lea'iding to the spring 53 of the out-oil relay R the norrnel eonteet of said spring being; oined by non (inctor54 W1 th the hetteryleed 1.8 connected.

- with the live pole of the central common battery 13. The forward content of sold spring 53 of the Glitz-Oil reio r H is joined. hy

branch oonduetor 55 with the lead from the second. common battery B he line signal S is oonneetocl upon one side with battery lend 23 and upon the other with eon duetor'ifileeding to normally closed soot-sets of the answering jock J, seiri. oontoets hei' g insulated from. the talking contents of the jack and thence by conductor 57 with the forward content of the spring 58 mounted upon the line relay R and which is joined, by another conductor 59 with e normal oonrelay R The line reley it is provided W1 th enedditionel s giringi 61 connected by e coir doctor 62 Witl i a normal contact of sold spring. of the cutoff relay it end the forward eontaet of whiel'i is connected through a suitable condiwtor 63 inolod ing s resistance 64 with the third conductor (:55 Whieh is eonneeted. with the test rings of the joolre and.

whioh inolmles the winding of the (rut-oil relay .ltflsmd relay being grounded at its opposite, terminal. The cord circuit is of the three strand type to cooperate with the three Wire line and inehu'les in addition to the tip strands t and t end the sleeve strands s and '8 the third strands 66 end 67, the strand 66 being connected. with the third conteot oi the answering plug P ineluii the windingof the supervisory relay r, end is connected by eonduotors (ill end fill w th the" live pole of the lmttterylii This relay adapted to olosethol'ocsl rirouit of the answering plug. A second supervisory relay 1 is connected by a, conductor 70 between conductor 68 and. the sleeve strnnde ol tho cord oirouit and is oriented to he eotuoted during oon'wrsotion to open the local oirruit oi the supervisory signal ii". A rerernlii poir of supervisory iroioys r and r ore ussorizttr-ul with the ceiling pluigwl."-", the Former being ernisi euitehly control the loeei eireriit oi the sniper visory signal S .ossoeieted with the ping P. The operetors set, inelueling the test reiey is the some are in. the GOMlBiIEUilZ oi the prerions figure, end. therefore, not speeilieeily deserihed, eithough it will he noted. 'thet this inetiinee'e, test reiey need not he of high reeis'tenee or impedenee, since the'teet eontorts oi the lines are not oonnee'ted. with the tolising eireni'ts. The ringing generator, however, is oriented to be oorn eoted'eeroes the 'inetelli'o eirenit oi the cord. eire'oit in the o eretion of the ringing hey, inetesiil olr' eon1- p etineeirtre, buttery eonneetion with the i seid sleeve strand es in 1, thi- 5 rendered unneeeessery since the on e l y" is in. seiri third. strend, which stir-ind is not ed in. the ooere ion. of rir ing;

l hen the snlisoriher o eell, the loing up his reeei rer completes enrrent no i. y over .ondneto 54, inri 5o, eondnetor ir iding the wind." 1g; 51 of the line relay, the no to the substation end. over the tip condoetor 2 and through. the winding 0 or the linereiey ii to ground. This eotuotes .5; line reloy, causing; it to close the eirouit oi the line signel S, wi'iirh may be traced from the hettery lead 23, tl'irougl'i the iron '1, eonduotor nor molly closed eonteets oi the ens" joek ll" rondne tor 57, EiPTlI 58, eonrlnetor 59 and spring 60 of the out-oil relsy it to ground. 'ihus the signal is lighted. end. et't'uets-the ottention oi the onerotor who inserts the answering pine; P oi her cord circuit and non-- neets her telephone with said eireu" to re eeiro the order. The operation oi the line ruler ii wlrien the subscriber nulls also results in (fl0t:7-ifi.g ll, peth vfor current in slmnt oi the ruli oll relay it, this poth being completed l'rmu cronduetor or; by means of wire 63, the

iorwo-rrl routeot and tuning til. of line r it, rm'nllirtrn: 62,, normel o vent e. 60 of the rut-oil relay ll. end shire out-oil" relay is prelemhly t about 500 ohms resistance, and the said resistenee eoil 65 i, which is pref rably non-iiuiuotive, is of only "i ohms-reeistiu 're, tin till ootoil' relay will 0 not he operated. by t \e oornaeoting oi the plug l. with the one. 'ering li', although by surh operation the third cont ate oi the plug and imnli nro hrougrl'it together and e oetl'i for current l'rolu the limiter-y ii provided over r'omluetors l8, (ill, (it? end 66, and thence lJy Wzrr oi e-mnhwtor (i5 'tl'irough soid relo gr end its mrollol poth. The normal. eonnr the hotter l? with the i'liliipllfli'll line there-- lore undisturhed and. the si-ihseriher not annoyedhy n. rhin'ie ol' potential of the our-- rent upon the oohoue ihe line 5' uel is retired ivy the or oi melting; the non .tion since the .ll{)ill'1tll]?' closed eon'tsots ig-nol. rireoit in. lhe jeelr are open, ins i'o'ndorin l nnl niert. At l, this time the so 'r'isory reloy r2 aiotnoted.

iii andion oi ill to close the local circuit of the supervisory signals, but since the subscriber s instrumentoff its hook, a second path for current is completed through the supervisory relay 1 and the sleeve strand 8 of the cord circuit, and over the telephone line, so that the local circuit of the signal is open and the lamp is prevented from operating. Upon finding that the wanted line is idle, the calling plug P is inserted in one of the multiple jacks J or J of the line and the ringing key is operated in the usual manner. The insertion of the said plug completes a path for current over the thread strand 67 from the live pole of the battery B and throu h said conductor 65, includin the winding 0 the cut-oii relay R to ground. This relay is not now shunted by the resistance 64 since the line relay R is not operated so that said cut-off relay is actuated and serves both to 0 en the local circuit of the line signal S am to 0 en the short circuit around itself. In addltion it disconnects the spring 53 from the conductor 54, thus severing connection with the battery 13 and connects it with the conductor 55 leading to the live pole of the battery B Thus when the subscriber responds his .line is char ed by current from the battery 13 whic flows over the line and through the windings of the relay R as before traced. The remainder of the o eration of connecting the lines, supervisin t e same and carryin on conversation will be readily understoo and it is'thought unnecessary to go into further details. It will be noticed that during conversation the lines are independently charged'with current from the separate batteries.

. windings 50 and 51 of the line relays may be of 100 ohms each.

While I have thus specifically described my invention which has been worked out for commercial urposes, I do not wish to be limited in. all respects to the specific details so described since it is obvious that various changes may be made without departing from the scope or principle of. the same.

What I claim and desire to secure by Letters Patent is:

1. In a telephone system, the'combination with a plurality of telephone lines, of a pair of sources of current at the central office, said lines being normally connected with oneof said sources to furnish current thereover when a subscriber is calling the central office, an operators' connective circuit to establish connections with the calling lines and without severing the normal connection of said source therewith, and further means whereby when connection is established with the called lines the said second source is connected therewith to furnishcurrent forconversation, substantially as described.-

2. In a telephone system, the combination with a plurality of telephone lines, a pair of sources of current at tne central office, the said lines being normally connected with. one of said sources which is adapted 'to furnish current thereover when the subscribers are calling, an operator's cord circuit, means to prevent a sudden or large change of potential upon the calling subscribers lines when a connection is established bythe cord cir cuit therewith, an means for connectin one of said sources with the calling lines an the other sources with the called lines during connections for conversation, substantially as described.

3. In a telephone system, the combination with a plurality of telephone lines, of a air of sources of electricit at the central o co, said lines being norma ly connected with one of said sources, an operator's cord circuit, means to prevent severing the normal connection with the lines that are calling the cens tral oflice when the cord circuit is connected therewith, and means to disconnect. said source from the lines that are called and to connect the other source with said latter lines when the connections for conversation are completed, substantially as described.

4. In a tele hone system, the combination with a plura ity of telephone lines of two sources of current at the central ofiice, said lines being normally connected with one only of said sources to furnish current thereover to, enable the subscribers'to signal the central office, said source also furnishing cur rent to the call lines for conversation, an operators cord circuit to establish connectrons for conversation between the lines, and 05 means for ap lying the other source to the called lines w ien connections are established therewith to furnish current thereo'ver for conversation, substantially as described.

5. In a telephone system, the combination 10 lines for, conversation and. with one of which sources the said lines are normally connected for signaling the central office, a cord circuit to establish connections between the lines for talking, and means whereby when the cord circuit is connected with the answering jacks said normally connected source remains connected with such lines and when the cord circuit is connected with the multiple jacks the sources being connected with said lines 130 through normally closed contacts of said relay to enable the subscribers to on crate their signalingdevices to call the central office, a cord circuit, and means whereby then the cord circuit is connected with the calling lines said relay contacts are undisl ubed and said source remains connected with such lines and when connection. is made with the called lines said relayis oper ted to disconnect. said source, the other source being at the same time connected with said called lines, sub-- stantially described.

7. In a telephone system, the combination with. a 'ilurality of telephone lines, of" a signaling device ands cut-oilF relay for each line, a pair of sources of electricity, one of said sources being connected. with said he a through the i'iormally closed contacts of said. relays to enable the subscribers to operate their signaling devices to call the central. olilice, a cord circuit, and means whereby when the cord circuit is connected with. the'calling lines said relaycontacts are undisturbed and said source remains connected with such. lines and when connection is made with the called lines the said relays of such lines are operated to disconnect said source and to connect the other source therewith, substantially as described.

8. In a telephone system, the combination with a lurality of telephone lines, of a signaling L evice and a cut-oil relay for eaclii line,

a pair of sources of electricity, one of said sources being; connected with said lines through the closed contacts of said relays to enable the subscribers to operate their naling devices to call the central ofl'ice, a cord circuit, and means whereby when the cord circuit is connected with the calling lines the cut o'll relaysof such lines reniain inoperative and source remains connected therewith and when connections is established with the called lines the cut-oll relays of such lines are operated to disconnect said source and to connect said other sourcetherewith, substantially as described.

9. a telephone system, the combination with a. plurality of telephone lines each having an answering jack and one or more inuh 'tiple jacks, of a signaling device and a cut-oil relay foreach line, a pair of sources of electrieity at the central. office to lurinsh current to the lines for conversation and with one of oft relays of such lines are operated to diswhich said lines are normally connected.

through contacts of said cut-oil relays "for signaling the central oiiice, a cord circuit to establish connections between the lines for tails ing, and means whereby when connection is established by the cord circuit with the air-- swering jacks the cutoff relays of suchlines are not operated. and said source remains connected therewith and when connection is established with title multiple jacl's the cutconnect said source and to connect said other source therewith, substantially described.

10. In a telephone system, the combination with a plurality of telephone lines, of a line relay and cut-oil relay for each. line, an answering jack and one or more multiple jacks or each line, a pair of sources oi electricity one of which is normally connected with the lines through the line relays and normal contacts of the cut-oil relays to lurnish current thereover for signaling cen tral oflice, a line signal for each line" the local circuit for each. of which includes normally closed contacts oil the answering jack and the cutoff relay of each line and normally open contacts of the line relay, cord circuit to establish connections with the lines for corn versation, and means whereby when. the cord circuit is connected with an answering jack in response to a call the local. circuit of the signal is opened at the answering jack contacts to retire the signal and. the cut-oil relayrernains inoperative to permit said normally connected source to remain connected with the calling line, and when the cord circuit is connected with the multiple of the called. for subscriber the said cut-oll relay is operated to open the local circuit and prevent the operation of the corresponding line signal and to disconnect said normally connected source and connect the other source with the said called line, substantially as described 11. In a telephone systen'l, the combination with a plurality of telephone lines, of a pair of common sources of electricity at the central cities, a cord circuit to connect of the lines together in'pairs for conversation,

and means for including said sources one to each line in every complete connection for conversation. between any of the lines, the

main .path for current from. said sources to the lines for the operation. of the substation transmitters not including the cord circuit, substantially as described.

12. in a telephonesystein, the combination with a plurality of telephone lines, of a lit? iie

pair of sources of electricity at the central otfice,a cord circuit to connect'any'ol the lines together for conversation, rneans for including said sources one to each line in every com-- plete connection for conversation between any two lines of the system, the main current from said sources being fed to the lines :l'or talking through the respective line" devices,

substantially as described.

13. In a telephone system, the combination with a plurality of telephone lines, of a line relay and a cut-oll relay for each line, a source of current with which said lines are coi'inectcd through the windings of the line relays and normal contacts of cut-off relays to enable the subscribers to call the central ofiice by opcriztting their line relays,

spring jacks connected with the lines on the substation side of the line re yer, a cord-pic euit having, its' two endsconrinctively dis-- continuous but inductively limited means. whereby when connection is established the. calling lines the said source remainscon.-

tion with a plurality of telephone lines, of a] nected therewith throughthe windings ofthe line relays and' when. connection is estali lished with the called for linessaidi'source is disconnected therefrom, and a second source. oficurrent connected with the called for-lines during conversation, substantially 'as de scribed.

. 14.. TIL-a telephone system, thecombine relays. and normal contacts. of. the cut-off re.

tion with a plurality of telephone lines, of aline relay and a cutoff relay-for each line, a sourceofi current withwhieh said lines are connected through the windings. of. the line lays to enable the subscribers to call the central office by operating their line relays, spring jacks-connected with the'lines on the substation side of the line relays, a cord circuit having its two ends. conductively discontinuous but inductively united, means whereby when connection is. established with the calling lines the said source remains connected therewith through the windings of the line relays and when connection is estab-.

lished with the called for lines said source is disconnectedtherefroin, and a second source of current connected with the called for lines during conversation, said first source being disconnected by the cut-off relays of' such. lines and the second source connected thereby also through the line relays windings, the

-said relay windings offering impedance. to

.voice currents. Y

15. In a telephone system, the combina tionwith a telephone line,'of a central source of sig'nalinI current asignal adapted to be.- actuated t e reby, a cut-off relay, a cut-ofl jack, and means to control the circuit of said signal either-at contacts of said jack or con- .tacts of saidcut-ofi relay, substantially as described.

16. In a telephone system, the combination with atelephone line, of a line signal therefor, a central source of signaling current a line relay for closing the circuit of said signal, a cut-ofl relay, a cut-off jack, and means to open the circuit of said line signal either at. the contacts of said jackor'at the contacts ofsaid cut-olf relay, substantially as described.

17. In a telephone system, the combination with a telephone line, of a line signal therefor, a line relay for closin the circuit of i said si me], answering and ca ling terminals forsaii line, cut-oll contacts associated with the answering terminal, a cut-off relay asso ciated with the calling terminals, .lneans to open thorn-cult of said signal at contacts of the ack when thecord circuit is connected 'with the answering terminal, and means to o 1 en the circuit ofsaid signal at contacts of ft e cut ofirelay when the cord is connected with a. calling terminal, substantially as tie--- scribedi. a

18.. In. a telephone system, the ccinliiha;

' oflice,.an c erators cord means where by when t e-cordoircuit is connected with a call' said line remainsundisturbed andifurtiun: means for disconnecting said source from the. 1 calledrfor line and for connecting said other line the connection of saidsource with source therewith throu the medium of the cord'circuit, substantial .y as described.

19. In a telephone system, the comhinm tion with a plurality of telephone lines, of'a pair of sources of electricit at the central office with one of which said lines are normally connected to enable the subscriber to call the central ofiiee, an o erators cord circuit, a cut-oi? relay for each me, meansassociated with each end. of the cord circuit to suit:

ably control the operation of said cut off rclays when connections are established with the lines whereb whenconnection is established with the caihng line the normal connection of the first named source of current therewith remains undisturbed and when connection is established with the calledfor lines said bat tery is disconnected therefrom, the secondhat-= terybeing at the same time connected with the latter lines, substantially as descrihed.

20'. In a telephone system, the comb netionwith a plurality of telephone lines, of two sources of direct current therefor, means for connecting one of said sources with ail of the telephone lines to furnish current fertile 3 line signaling apparatus, and means when two lines' are placed in condition for center sation, Where the talking current for the calling line is, furnished from said first source and the talking current for the called line is furnished from the other source, sub stantially as described,

21. In a telephone system, the combination with a plurality of telephone lines, of a line relay for each of said. lines, two sources of di rect current adapted to be associated with said line relays, means for connecti 5 one of said sources with alto)? the telephone hues to furnish current for the line signaling apparatus, and means when two lines are placed in condition for conversationwhereby said first source remains in crmnec-tion with me callin line through the coils of said line reiay, and

whereby said second sourceis connected with the called hue through the rolls of its line relay, substantiaily described.

22. in a telephone system, the combina-- 'tion with a plurality of telephone lines, of

is furnishecl' to the send line relay according to whether thehne I 23. Ina- 't' two sources of direct current for said lines, of

a. line Tele'y for each of said lines, said relay.

having two windings, and means whereby current from one or the other of said sources lme through both coils of is a, calling or a eallecltelephone line,' sub stentinlly an 'e oi'ihed.

el hone System11,

tion with a plilmlity ol telephonelines, 01' a.

out-oil relay "for each of said lines-1, two sources of our-rent for soul lines at the con-- tral oillioe means whereby ener r from one of said so'urgee may be normally maintained on all of said lines through the contacts 0! soul eut-of relay, and turther nemis whentwo lin as are placed. in condition {or convensation whereby one ol said lines is e'liseonnested iroin said. source and enmi'xeeterl to the other source through tlte contacts of its out off releyi, substantially as described.

24'. In a telephone system, the combination with a plurality of telephone lines, of e cut-olf relay associated with each 01" said: lines, two sources of current for said lines" at the central office, means whereby energy from one of said sources is normally maintained on all of said lines through the oontz'icts of its who'll relay, and further means when two lines are pieced in condition for conversation whereby energy from the other of said sources is maintained on one of said lines through the contacts of its cutoil relay, substantially as described.

Signed by me at Chico- 0, county of Cook, 35 State of Illinois, this sixtli (lay of November 1903.

HOWARD M. POST.

1 E. A. GARLOGK. 

